The ongoing epidemic of cholera in Haiti is one of the largest of the last decade and is representative of a growing burden of epidemic cholera. Remarkably little is known about immune responses to cholera and oral cholera vaccines in immunologically nave populations, and in populations outside of historically cholera endemic areas of Asia. Of paramount importance, all decisions regarding the use of cholera vaccine have been made using immunogenicity and efficacy data generated in areas of the world where cholera has long been entrenched and where cholera vaccine may be boosting anamnestic immune responses in previously exposed individuals. Therefore, assessment of vaccine immunogenicity and effectiveness during the roll out of Shanchol in Haiti provides the unique opportunity to directly inform vaccine strategies. Almost nothing is known about the relationship between HIV and cholera, despite the fact that the largest number of cholera cases reported to WHO are now from Sub-Saharan Africa. Here, we propose to characterize immune responses to oral cholera vaccines and to V. cholerae infection in Haiti -- a previously immunologically nave population with host and epidemiologic features that are reflective of populations experiencing cholera epidemics in recent years. We also directly assess the efficacy of the oral cholera vaccine, Shanchol, in Haiti, and evaluate the inter-relationship between HIV and V. cholerae infection and vaccination. Our collaborative team is deeply involved in the cholera vaccine roll-out in Haiti and is uniquely situated to perform the proposed studies.